Variable resistance memory devices store binary data as two different resistance values, one higher than the other. Variable resistance memories differ from DRAMs in that they represent a binary value as a resistance of a resistive memory element rather than as a charge on a capacitor. The resistance value represents a particular binary value of logic “0” or logic “1”. Variable resistance memories are non-volatile, where the capacitor structures employed in DRAMs are volatile. When sensing the resistance value of a variable resistance memory device, it is possible to compare the resistance of a memory cell undergoing a read operation with resistance of a reference cell to determine the resistance value of the cell being read and thus its logic state. However, if the reference cell is defective and a column of memory cells within an array uses the same defective reference cell, the entire column of memory cells will have erroneous resistance readings. In addition, specialized circuitry is required to set the resistance value of a reference cell, and a sense amplifier circuit for such an arrangement tends to be complex and large.
Also, sensing schemes for variable resistance memory devices typically have a unique architecture which is different from that employed in typical DRAM circuits. Large volumes of DRAMs are produced and DRAM sensing technology is well developed. Devices employing DRAM sensing technology, thus benefits from technological maturity and efficiencies of manufacturing scales. Therefore, it is desirable for the read and write circuit of resistance memory devices to be as similar as possible to those of existing DRAM memory devices.